Noise filling in perceptual transform audio coding

Abstract

Noise filling in perceptual transform audio codecs is improved by performing the noise filling with a spectrally global tilt, rather than in a spectrally flat manner.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of copending International Application No. PCT / EP2014 / 051631, filed Jan. 28, 2014, which claims priority from U.S. Application No. 61 / 758,209, filed Jan. 29, 2013, which are each incorporated herein in its entirety by this reference thereto.BACKGROUND OF THE INVENTION[0002]The present application is concerned with noise filling in perceptual transform audio coding.[0003]In transform coding it is often recognized (compare [1], [2], [3]) that quantizing parts of a spectrum to zeros leads to a perceptual degradation. Such parts quantized to zero are called spectrum holes. A solution for this problem presented in [1], [2], [3] and [4] is to replace zero-quantized spectral lines with noise. Sometimes, the insertion of noise is avoided below a certain frequency. The starting frequency for noise filling is fixed, but different between the known technology.[0004]Sometimes, FDNS (Frequency Domain Noise Shaping) i...

AI Technical Summary

Benefits of technology

This approach improves the quality of the noise-filled audio signal by reducing the detrimental effects on tonal parts and enhancing the audio quality by compensating for the spectral tilt caused by subsequent shaping, resulting in a more pleasant and accurate reproduction of the audio signal.

Problems solved by technology

In [3] it is noted that there is a problem of a compromise between the granularity of the noise filling and the size of the necessitated side information.

There are other problems beyond the above discussed ones, which result from the noise filling concepts known so far, according to which noise is filled into the spectrum in a spectrally flat manner.

The inventors of the present application, however, realized that this tilt in the finally reconstructed spectrum negatively affects the audio quality, because it leads to spectral holes remaining in noise-filled parts of the spectrum.

In other words, whenever the audio signal has a tonal content, the noise filled into the audio signal's spectrum leaves the tonal peaks of the spectrum unaffected by keeping enough distance therefrom, wherein however the non-tonal character of temporal phases of the audio signal with the audio content as non-tonal is nevertheless met by the noise filling.

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